CLIMATE-CHANGE AND NATURAL-RESOURCE DYNAMICS OF THE ATACAMA ALTIPLANODURING THE LAST 18,000 YEARS - A PRELIMINARY SYNTHESIS

Interaction between anticyclonic air masses, the effect of the cold Hu mboldt current, and the moisture barrier of the mountain chain results in extremely dry environmental conditions on the western slope of the Atacama Andes. Even the highest peaks above 6,700 m in the continuous permafrost belt are currently free of glaciers, and modern recharge o f the water cycle is restricted to small catchments at high altitude. The vegetation between 3,100 and 4,800 m is too sparse to initiate any soil formation. The temperatures of the last cold maximum (18 kyr B.P ) were probably 7-degrees-C lower than today. The late-glacial period (17-11 kyr B.P.) was characterized by 5-10 m higher lake levels, indic ating a large increase in precipitation at latitude 23-24-degrees Sout h. The early Holocene (11-7 kyr B.P.) experienced wetter conditions an d summer temperatures 3.5-degrees-C higher than today, together with s ignificant groundwater recharge. This provided favorable conditions fo r an early hunter-gatherer economy. After about 3000 B.P. conditions b ecame drier; intensive pastoralism may have added to the impacts on ve getation cover, and groundwater recharge was curtailed. Natural resour ce management policies must take into account the dynamics of a changi ng environment. Present-day reliance on groundwater for mining, urbani zation, and agriculture cannot be sustained, for supplies are believed to be fossil water, or else the recharge rate is so slow that actual use may far exceed replenishment.